The present invention relates to a charging generator apparatus to be driven by, for instance, an engine mounted on an automobile.
FIG. 4 is a circuit diagram of a conventional charging generator apparatus, wherein a reference numeral 1 designates a generator to be actuated by an engine (not shown) which comprises armature windings 101 having a three-phase star connection and a field winding 102, a numeral 2 designates a three-phase full-wave rectifier for rectifying the a.c. output voltage of the generator 1, a numeral 3 designates a voltage regulator which detects the output voltage of the three phase full wave rectifier 2 and turns on or off a transistor 301 to thereby control a field current flowing in the field winding 102 so that the output voltage of the generator 1 is maintained to be a predetermined level, and a numeral 4 designates a battery to be charged by the output voltage of the three-phase full-wave rectifier 2.
The operation of the conventional charging generator apparatus will be described. When the generator 1 is actuated by the engine (not shown), a three-phase a.c. voltage is induced in the armature windings 101 since a field current is passed from the battery 4 through the field winding 102 and the transistor 301. The three-phase phase a.c. current is rectified by the three-phase full-wave wave rectifier 2 and charges the battery 4. When the output voltage of the generator 1 is higher than a predetermined level, the voltage regulator 3 interrupts the field current by turning off the transistor 301, whereby the output voltage of the generator 1 is reduced. Then, when the output voltage of the generator 1 is lower than the predetermined level, the voltage regulator 3 turns on the transistor 301 so that the field current is passed through the field winding 102, and the output voltage of the generator 1 is again increased. Thus, the generator 1 charges the battery 4 by a predetermined voltage.
The conventional charging generator apparatus requires a requesite number of turns of the armature windings in order to obtain a predetermined revolutional speed for initiating power generation. When the number of turns of the armature windings 101 is determined, the maximum output current at a high speed revolution is converged to a current value determined by the armature reaction as is well known. Namely, there has been known that a field current is increased by a method as disclosed, for instance, in Japanese Unexamined Patent Publication No. 285698/1987 in order to assure the ability of charging at a low speed and to obtain a high output current at a high speed revolution. In this case, the copper loss, which is known as I.sup.2 R, of the armature windings is increased in proportion to the square of the output current when the output current is increased. This causes a large temperature rise, resulting in the lack of reliability.